1. Field of the Invention
The present invention relates to a coating film of material which comprises amorphous carbon, has high hardness, high oxidation resistance, high thermal resistance, high electric resistance and high thermal conductivity, and a method and apparatus for producing the same.
2. Description of the Prior Art
It is well known that plastic material and common metal are susceptible to surface scratch so that the surfaces initially having excellent luster gradually lose the luster and damage an appearance.
This has been considered to be due to the fact that these plastic material and metal are relatively soft and have low abrasion resistance.
Means heretofore used for overcoming these disadvantages include the application of hard and thin-film coating to the surface of material having soft surface such as cutting tool, bite etc. to provide durable and lustrous surface and industrially the application of extreme hard film to the surface to make them durable for a long period of time, and recently studies have been made on the application of coatings of silicon carbide and boron nitride to the surfaces of bite to provide more excellent surface materials. However, these methods still leave some disadvantages to be desired.
Also, in the case of material which when contacted with heat or oxygen will be decomposed or react to change the properties as well as protective coating film such as antioxidation coating film applied to the surface of electronic equipment devices (e.g., GaAs semiconductor, ZnS EL device and HgCdTe infrared sensor element) which are required to operate stably for a long period of time, it is essential to have recourse to material and method which permit the application of surface coating at relatively low temperature.
Also, considering the case of solar cell comprising amorphous silicon, etc., containing large amount of hydrogen or large amount of hydrogen and fluorine, the cell essentially has low energy converting efficiency and is compensated for by means of the increased area or the like. However, there still exists a need for the development of materials of higher efficiencies for the surface coating films in view of the necessity to ensure a sufficient amount of incident -ight to the solar cell.
On the other hand, from the standpoint of ensuring a sufficient durability for the component parts subjected to severe wear, e.g., the bearing of rotary member, and gear, the abrasion resistant coatings which have presently been used are insufficient and there is a need for coatings of longer durability.
Considering again the case of semiconductor, the conventional silicon semiconductors are subject to limitations that the forbidden band gap is as narrow as 1.21 eV and they cannot be used at high temperature thus giving rise to a need for the development of material having wider range of working temperatures.
The conventional sputtering methods include one in which an argon plasma is produced by applying a voltage across an anode and a cathode in any argon gas or the like of about 0.133 to 1.33 Pa (10.sup.-3 to 10.sup.-2 Torr) and a target material is sputtered by the argon ion thereby forming an alloy coating on a substrate.
An example of the sputtering apparatus used with the above-mentioned conventional technique is disclosed for example in U.S. Pat. No. 4,431,562.
With the technique of forming a high-hard amorphous carbon film of high electric insulating quality by the sputtering process, increasing the input power is effective for the purpose of preventing the occurrence of defects in the coating film, increasing the rate of film formation and so on.